Method of making an electronic grid



June 6, 1956 w. E. GLENN ET AL 2,751,662

METHOD OF MAKING AN ELECTRONIC GRID Filed Oct. 2 1951 Ill/IA 32 IILM. A

FIG- 7.

INVENTORS. W/LL/AM E GLEN/v y EARL W. HOSTETTER AT TOR/VEY.

United States Patent 6 ll/IETHOD OF MAKING AN ELECTRONIC GRID William E. Glenn and Earl W. Hostetter, Berkeley, Calif., assignors to the United States of America as represented by the United States Atomic Energy Commission Application Gctober 2, 1951, Serial No. 249,374

4 Claims. (Ci. 29--25.17)

The present invention relates to an improved grid construction and method of making same and in particular to a grid for use in electronic equipment having parallel wires and maintaining such parallelism when in use in such as a klystron or the like.

Many of the new electronic vacuum tubes and even gas tubes employ flat parallel electrodes rather than cylindrical electrodes and the production of fiat grid electrodes with parallel wires has proven quite difiicult, particularly where large diameter grids are required. Conventionally fiat grids are formed by gold soldering tungsten wires to a supporting ring; however, difficulty is experienced in holding the wires in parallel relationship during this process. Also heating and cooling of the wires and ring during soldering causes a warping of the ring and a certain amount of sag in the wires which is highly undesirable. Distortion of the ring after attachment of the wires, as by hammering, may be used to stretch the wires; however, this generally results in the individual wires lying in different planes and also results in a large percentage of breakage, often as high as 50%.

would result during operation thereof.

It is therefore an object of the present invention to provide a new and improved electronic grid and method of construction thereof.

'It is another object of the present invention to provide a new and improved electronic grid having parallel wires .under tension and lying in a single plane.

It is a further object of the present invention to provide a new and improved method of making an electronic grid without the application of heat thereto.

It is still another object of the present invention to provide'an improved electronic grid structure of large diameter.

The present invention provides for imbedding line wires .in a support ring in such a manner that they are maintained in tension, and this is accomplished by preparing the surface of the supporting ring so that the same force which .imbeds the wires therein also causes a radial shifting of the surface to stretch the isnbedded wires.

Considering now the invention in some detail, referonce is made to the accompanying drawings wherein:

Figure l is an isometric View of the grid support ring; Fig. 2 is a cross section view of the support ring taken at 22 of Fig. 1 ant. showing the cutting tool used on i the support ring;

Fig. 3 is an isometric view of the mandrel employed to contain the grid wires during the process of securing "them to the support ring;

2,751,662 Patented June 26, 1956 Fig. 4 shows the mandrel in place on a lathe employed to wind the wire on the mandrel;

Fig. 5 shows the mandrel and rings in place in a hydraulic press;

Figs. 6 and 7 are sectional views of the mandrel and support ring during the process of fixing the wires;

Fig. 8 is a sectional view of a portion of the support ring and attached wires;

Fig. 9 shows the grid structure after wire fixation; and

Fig. 10 shows the completed grid.

Proceeding now with a description of the improved method of grid manufacture, there is first formed an annular support ring 11 which may be cut from a tube of appropriate wall thickness upon a lathe for example. Ring 11 is preferably formed of a relatively soft or malleable metal, such as copper, and has at least one smooth face 12 which is accurately machined so that it lies in but a single plane. There is next formed upon the smooth face 12 of ring 11 a spiral cut 13 having a plurality of turns, and this may be best accomplished by placing ring 11 in a lathe chuck and driving a cutting tool 14 inwardly across ring face 12 at a constant speed while ring 11 is rotating in the lathe chuck. Cutting tool 14 has a specially ground sharp point and is set at an angle in the lathe tool mount so that one edge of tool 14 is slightly off perpendicular to the surface of ring face 12 and the cut therein slants away from the center of ring 11. The turns of spiral cut 13 are made quite close together; for example, with a ring wall thickness of A5 to /1 inch, five to ten turns may be made with a depth of cut of about .015 inch. intermediate adjacent turns of spiral groove 13 there are formed lands 15 which extend over the perpendicular edge of the adjacent turn of the spiral groove 13 so that upon completion groove 13 is actually undercut. As cutting tool 14 passes over face 12 of ring 11 the heel of the tool deforms the adjacent land so that it is forced over the perpendicular edge of the adjacent turn of groove 13 and the perpendicularly cut edge of groove 13 is tipped to slant away from the center of ring 1 as shown in Fig. 2. By following the above-described steps of grooving the face of a malleable metal with a pointed cutting tool held at an angle to the face of the work the land deformation automatically results and the desired groove configuration is obtained.

At this point it should be noted that the configuration of support ring 11 is not limited to circular and square, octagonal or various other shapes may be used. Also, the cutting of groove 13 may be performed by other than a lathe, as for example by a shaper or milling machine and it is further possible to provide slanted lands by the use of a small grinding machine which cuts a sloping groove and in such case the lands would originally slant with deformation.

In the attachment of grid wires to support ring 11 there is employed a mandrel 16 as shown in Fig. 3. Mandrel in has two flat parallel faces 1! and 18 and may be formed in a plate shape with a shaft or handle 19 extending from one edge thereof parallel to faces 17 and 18. Two opposite edges of mandrel 16 are rounded or curved and relief grooves 21 and 22 are formed therein and extending substantially parallel to faces 17 and 18 for the length thereof. There is also provided on opposite curved edges of mandrel 16 a plurality of small notches 23 which are spaced equidistant apart, a distance equal to the desired grid wire spacing. Upon man drel 16 there is wound the grid wire 24 which is prefer ably tungsten or the like and winding of mandrel 16 may be accomplished by placing mandrel shaft 19in the chuck of a lathe and threading wire from a spool over a pulley and through an eye as in the lathe tool holder onto mandrel 16, as shown in Fig. 4. The lathe chuck is then rotated and the tool holder moved at a constant speed, which is related to the rotational speed of the lathe chuck and the spacing of notches 23 on mandrel 16 so that wire 24 is wound upon mandrel 16. Wire 24 is secured at each end to mandrel 16, and the grid is then ready for wire fixation. 1 V

Attachment of grid Wire 24 to support ring 11 is made by pressure as in a hydraulic press 26, Fig. 5; There is provided on hydraulic press 26 a pair of opposing jaws or anvils 27 and 28 having opposite circular bosses 29 and 31, respectively. The diameters of bosses 29 and 31 are equal to the inner diameter of grid support ring 11 and there is placed upon lower anvil 28 a support ring 11 which fits over boss 31 thereby restraining ring 11 from lateral movement. An annular squeeze ring 32 having a larger'diameter than support ring 11 is placed on lower anvil 28 about ring 11, and mandrel 16 is positioned above support ring 11. Squeeze ring 32 has a greater axial depth than support ring 11 and thus mandrel 16 rests on squeeze ring 32 without touching support ring 11; squeeze ring 32 being formed of rubber or 'the like so as to be readily deformable under pressure whereby mandrel 16 may be urged downward into contact with support ring 11. A second support ring 11 is placed about boss 29 on upper anvil 27 and maintained thereon as by grease or other adhesive means and a second identical squeeze ring 32 i placed between mandrel 16 and upper anvil 27. With this combination in place between anvils 27 and 28 of hydraulic press 26 the grids are ready for wire fixation. It is noted that in the abovenoted combination, grid wire 24 is not in contact with support rings 11 and thus there is no possibility of displacing the turns of wire 24 on mandrel 16.

In the process of connecting grid wires 24 to support rings 11, hydraulic press 26 is operated to force anvils 27 and 28 together as shown in detail in Figs. 6 and 7. Squeeze rings 32 are deformed and flattened out by the pressure exerted on anvils 27 and 28 and mandrel 16 is urged into forceable contact with support rings 11. The first consequence of the contact between mandrel 16 and support rings 11 is the forcing of hard grid wire 24 into the faces 12 of the fairly soft support rings 11. Additional pressure exerted by press 26 causes mandrel 16 to bear directly upon surfaced faces 12 of support rings 11 and because of the configuration of the lands 15 they deform radially outward of ring 11 as shown in Figs. 7 and 8. Thus, the face 12 of support ring 11 effectively moves away from the center of ring 11 and as wire 24'is imbedded therein, this wire is put in tension and stretched.

While support rings 11 and mandrel 16 are in intimate contact and before the pressure exerted on the combination by press 26 is released, the wire 24 is relieved by cutting. This may best be accomplished by passing a sharp instrument 33 along the relief grooves 21 and 22 in two opposite sides of mandrel 16. With wires 24 out they are no longer attached to mandrel 16 and press 26 is then opened and mandrel 16, squeeze rings 32 and support rings 11 and attached wires 24 removed.

It is desirable to finish the electronic grid 34 formed by the above method by cutting off the ends of wires 24 extending beyond the outer edge of support ring 11. This may be accomplished by a hand file 35 or a grinding operation which not only severs the extraneous wire .but also turns the ends of the wires downward and forces them into the edge of support ring 11 as shown in Fig. 8. {It will be appreciated that the foregoing process pro- I duces a grid structure having the wires thereof in strict parallelism and lying in a single plane. Also the grid wires 24 are in tension across support ring 11 and thus remain taut even though heated. It should be further .noted that mandrel 16 is formed of a hard metal such as steel and thus is not affected or in any way deformed .during the grid construction and may thus be used re-.

.P t t ;wi he. p rec at d tha h confi u a io o the shape of support ring 11 and, of course, various shapes of anvils 27 and 28 may be used to hold rings 11. Also 'the spacing of grid wires 24 is dependent upon their disposition on mandrel 16 so that various mandrels with differently spaced notches 23 may be employed to form grids with desired wire separation.

While the present invention has been described with respect to a single embodiment and in terms of particular steps in the process, it will be apparent that numerous modifications and variations are possible within the spirit and scope of the invention and thus it is not intended to limit the invention except by the terms of the following claims.

What is claimed is:

l. A method of forming an electronic grid comprising the steps of cutting a flat end on an annular ring of relatively soft metal, cutting a spiral groove in the flat end of said ring with a sharply pointed cuting tool held at an angle to the cutting surface whereby the lands formed between adjacent turns of the spiral groove slope radially outward, winding a hard wire about a hard flat plate in parallel turns, forcing a face of said Wire wound plate against the flat end of said annular ring whereby said wires are imbedded in the surface of said ring and the lands on the end thereof bend radially outward to place said wires in tension, cutting said wires free from said flat plate, and shearing oil the loose ends of wire extending beyond said annular ring.

2. A method of forming an electronic grid having parallel grid wires lying in a single plane and comprising forming a support ring of a malleable material and having a flat end surface, cutting a spiral groove in the flat surface of said support ring with lands intermediate adjacent turns of said spiral slanting radially outward on said ring, Winding a grid wire about a mandrel having a flat surface with the turns of said wire winding being separated and parallel, said mandrel and wires being formed of a material that is hard relative to the support ring, forcing the flat side of said mandrel against the flat end surface of said support ring whereby said wires are imbedded in the surface of said support ring, further urging said mandrel and support ring together to deform the lands on said support ring radially outward and place the grid wires in tension, cutting the grid wires loose from said mandrel and trimming the ends of said wires about said support ring.

3. A method of constructing a grid structure having parallel wires and comprising cutting an annularsupport ring from a tube having a small wall thickness, cutting a spiral groove upon one end of said support ring and having a plurality of turns defining lands therebetween, said groove being slanted from the surface radially inward of said ring whereby said lands slant radially outward, winding grid wire about a mandrel having a flat surface larger than the diameter of said support ring, said grid wire and mandrel being formed of a harder material than the material of said support ring, disposing said mandrel adjacent said support ring with the flat surface of said mandrel facing the grooved end of said support ring and said mandrel resting upon a readily deformable support, forcing said wire wound mandrel and support ring in contact and applying pressure't'hereto to imbed the grid wires in said support ring and deform the lands thereof radially outward whereby said grid wires are placed in tension, cutting said grid wires from said mandrel, releasing the pressure upon said mandrel-ring contact, and removing said mandrel from said support ring and attached grid wires.

4. A method of constructing an electronic grid comprising forming a flat surface on an apertured member to contain the grid, cutting a plurality of adjacent grooves on said flat surface with the lands between said grooves slanting away from the aperture, winding a grid wire on a mandrel to form a parallel wire formation on a flat face thereof, placing the flat face of said mandrel against the fiat surface of said apertured member and applying pressure thereto, said apertured member being formed of a softer material than said wire and mandrel whereby said wire is imbedded in the surface of said apertured member across the aperture therein and the lands on the flat surface are deformed in a direction away from the aperture to place the grid wire in tension, and releasing the grid wire from said mandrel whereby said apertured member contains a grid across the aperture therein formed of parallel wires in tension.

References Cited in the file of this patent UNITED STATES PATENTS Vance Sept. 29, 1942 Hirmann July 31, 1945 Bondley Jan. 25, 1949 Zetka June 7, 1949 Drieschman Aug. 22, 1950 Borland et a1. Sept. 16, 1952 FOREIGN PATENTS Great Britain Dec. 6, 1944 

1. A METHOD OF FORMING AN ELECTRONIC GRID COMPRISING THE STEPS OF CUTTING A FLAT END ON AN ANNULAR RING OF RELATIVELY SOFT METAL, CUTTING A SPIRAL GROOVE IN THE FLAT END OF SAID RING WITH A SHARPLY POINTED CUTING TOOL HELD AT AN ANGLE TO THE CUTTING SURFACE WHEREBY THE LANDS FORMED BETWEEN ADJACENT TURNS OF THE SPIRAL GROOVE SLOPE RADIALLY OUTWARD, WINDING A HARD WIRE ABOUT A HARD FLAT PLATE IN PARALLEL TURNS, FORCING A FACE OF SAID WIRE WOUND PLATE AGAINST THE FLAT END OF SAID ANNULAR RING WHEREBY SAID WIRES ARE IMBEDDED IN THE SURFACE OF SAID RING AND THE LANDS ON THE END THEREOF BEND RADIALLY OUTWARD TO PLACE SAID WIRES IN TENSION, CUTTING SAID WIRES FREE/FROM SAID FLAT PLATE, AND SHEARING OFF THE LOOSE ENDS OF WIRE EXTENDING BEYOND SAID ANNULAR RING. 